Eriksson A W
Institute of Human Genetics, Free University of Amsterdam, The Netherlands.
Acta Genet Med Gemellol (Roma). 1990;39(3):279-93. doi: 10.1017/s0001566000005195.
A study was conducted on twinning in relatives of consecutive triplet sets in the Aland Islands in the years 1740-1939. The incidence of twinning in sibships of triplets was extremely high, 80/1000 (56/1000 before and 143/1000 after the triplet maternity). In Finland as a whole, 1905-1954, the twinning rate was among mothers of triplets 38/1000, ie, about 2.6 times the rate in general population, and was higher after (48/1000) than before the triplet maternity (34/1000). In the sibships of fathers of triplets there was a low rate of twinning (below 10/1000) both of same-sexed (SS) and of opposite-sexed (OS) triplets. Among sibships of mothers of OS triplets the twinning rate was 18/1000 and among mothers' sibships of SS triplets 26/1000. The series of triplet families from both Aland and Finland as a whole indicate a considerably higher frequency of twinning on the maternal than on the paternal side. The sibships of OS triplets in Finland have higher twinning rates than sibships of SS triplets (50/1000 vs 27/1000). In sibships of triplets, not only the DZ but also the MZ twinning rates were approximately twice as high as those in the general population. The triplet rates in Finland were increasingly strong with maternal age and were in the last century among mothers of 30-39 years of age considerably higher than among mothers from this century. This, in combination with higher mean parity, may explain the high rates of multiple maternities in sibships of triplets in the past. The rate of triplet maternities seems to be more sensitive to sociodemographic changes than the rate of twin maternities. Mothers of triplets in Finland had a high frequency (more than 40%) of prenuptially conceived firstborn children. This, and a short protogenesic interval indicate that triplet-prone mothers are more fecundable, ie, they conceive with greater ease and/or may have a better physical condition than other women for completing a gestation with multiple embryos.
1740年至1939年间，对奥兰群岛连续三胞胎家庭的亲属中的双胞胎情况进行了一项研究。三胞胎同胞中的双胞胎发生率极高，为80/1000（三胞胎母亲生育前为56/1000，生育后为143/1000）。在1905年至1954年的整个芬兰，三胞胎母亲中的双胞胎发生率为38/1000，即约为普通人群发生率的2.6倍，且生育后（48/1000）高于生育前（34/1000）。在三胞胎父亲的同胞中，同性（SS）和异性（OS）三胞胎的双胞胎发生率都很低（低于10/1000）。在OS三胞胎母亲的同胞中，双胞胎发生率为18/1000，在SS三胞胎母亲的同胞中为26/1000。来自奥兰群岛和整个芬兰的三胞胎家庭系列表明，母亲一方的双胞胎发生率远高于父亲一方。芬兰OS三胞胎的同胞比SS三胞胎的同胞有更高的双胞胎发生率（50/1000对27/1000）。在三胞胎同胞中，不仅双卵双胞胎（DZ）而且单卵双胞胎（MZ）的发生率都大约是普通人群的两倍。芬兰的三胞胎发生率随母亲年龄增长而越来越高，在上个世纪，30至39岁母亲的三胞胎发生率远高于本世纪的母亲。这与较高的平均产次相结合，可能解释了过去三胞胎同胞中多胎生育的高发生率。三胞胎生育的发生率似乎比双胞胎生育的发生率对社会人口变化更敏感。芬兰的三胞胎母亲中，婚前受孕的头胎孩子频率很高（超过40%）。这一点以及较短的初孕间隔表明，易生三胞胎的母亲更易受孕，也就是说，她们比其他女性更容易受孕，和/或在怀有多个胚胎的情况下完成妊娠时身体状况可能更好。
